The systems and methods herein relate to the operation of a particle filter, within an exhaust-gas path of an internal combustion engine that is coupled to an exhaust-gas aftertreatment device which may be operated in accordance with a method of operation of a motor vehicle.
In wall-flow particle filters, such as soot filters in internal combustion engines, solid material is filtered out of exhaust gas stored on the wall of the substrate of the particle filter. Particles removed by a properly functioning filter from exhaust gas reduce undesirable emissions to meet emissions and operation standards.
The continuous operation of a particle filter may be limited by its absorption capacity. A process called regeneration allows the filter to be restored to its original absorption capacity and operating efficiency without replacing the filter. Regular regeneration allows the filter to continuous and consistent operation. Further, extended use of a particle filter may contribute to counter-pressure within the exhaust system resulting from an increasing impermeability of the filter as the amount of solid particle content increases. An increase in engine load from exhaust-gas counter-pressure exerted on the engine by the filter may also be alleviated by restoring filter permeability via a regular regeneration.
During the regeneration of the particle filter, the solid material deposited in the particle filter is burned off. The combustion process may be initiated in a targeted manner by introducing within the exhaust system a rich fuel mixture in which air-to-fuel ratio is decreased so that exhaust gas contains still-unburned fuel after combustion and prior to entering the particle filter. The presence of unburned fuel may trigger a secondary combustion within the filter. Regeneration may also be initiated by introducing very high heat into the exhaust system.
If the regeneration is not performed regularly in order to limit the amount of deposited solid material, a spontaneous combustion may occur, which may degrade the filter and engine. During the combustion process, temperatures of over 600 degrees Celsius may be reached, which may degrade the substrate of the particle filter. The risk of damage is particularly high if the combustion process takes place in an uncontrolled manner that may be initiated, for example, by an unexpectedly high amount of deposited solid material. It is therefore desirable to keep the interval between two regenerations below a threshold. However, regular controlled regeneration cycles increase the fuel consumption. Further, regeneration may not be possible in all operating conditions.
The inventors found that by supplying ambient air to the exhaust gas path at a rate dependent on a measured mass airflow rate (MAF) and/or filter temperature, uncontrolled regeneration may be abated. This is because the mass flow rate of the exhaust-gas flow is generally a function of the presiding operating state of the internal combustion engine producing the exhaust-gas flow. Additionally, the temperature within the filter is generally indicative of the impending of potential spontaneous regeneration. Thus, by allowing ambient air to enter the filter at a controlled rate the cooling of the filter may be controlled, particularly in situations that may contribute to spontaneous regeneration.
It should be understood that the background and summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.